Evidence for mass accretion driven by spiral shocks onto the white dwarf in SDSS J123813.73-033933.0. (arXiv:1811.05981v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Pala_A/0/1/0/all/0/1">A. F. Pala</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gansicke_B/0/1/0/all/0/1">B. T. Gänsicke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marsh_T/0/1/0/all/0/1">T. R. Marsh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Breedt_E/0/1/0/all/0/1">E. Breedt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hermes_J/0/1/0/all/0/1">J. J. Hermes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Landstreet_J/0/1/0/all/0/1">J. D. Landstreet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schreiber_M/0/1/0/all/0/1">M. R. Schreiber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Townsley_D/0/1/0/all/0/1">D. M. Townsley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_L/0/1/0/all/0/1">L. Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aungwerojwit_A/0/1/0/all/0/1">A. Aungwerojwit</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hambsch_F/0/1/0/all/0/1">F.-J. Hambsch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Monard_B/0/1/0/all/0/1">B. Monard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Myers_G/0/1/0/all/0/1">G. Myers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nelson_P/0/1/0/all/0/1">P. Nelson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pickard_R/0/1/0/all/0/1">R. Pickard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Poyner_G/0/1/0/all/0/1">G. Poyner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reichart_D/0/1/0/all/0/1">D. E. Reichart</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stubbings_R/0/1/0/all/0/1">R. Stubbings</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Godon_P/0/1/0/all/0/1">P. Godon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Szkody_P/0/1/0/all/0/1">P. Szkody</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martino_D/0/1/0/all/0/1">D. De Martino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dhillon_V/0/1/0/all/0/1">V. S. Dhillon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Knigge_C/0/1/0/all/0/1">C. Knigge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Parsons_S/0/1/0/all/0/1">S. G. Parsons</a>
We present high-time-resolution photometry and phase-resolved spectroscopy of
the short-period ($P_mathrm{orb} = 80.52,mathrm{min}$) cataclysmic variable
SDSS J123813.73-033933.0, observed with the $mathit{Hubble}$ $mathit{Space}$
$mathit{Telescope}$ $mathit{(HST)}$, the $mathit{Kepler/K2}$ mission and the
Very Large Telescope (VLT). We also report observations of the first detected
super-outburst. SDSS J1238-0339 shows two types of variability: quasi-regular
brightenings recurring every $simeq 8.5$ h during which the system increases
in brightness by $simeq 0.5$mag, and a double hump quasi-sinusoidal modulation
at the orbital period. The detailed $mathit{K2}$ light curve reveals that the
amplitude of the double-humps increases during the brightenings and that their
phase undergoes a $simeq 90^{circ}$ phase shift with respect to the quiescent
intervals. The $mathit{HST}$ data unambiguously demonstrate that these
phenomena both arise from the heating and cooling of two relatively large
regions on the white dwarf. We suggest that the double-hump modulation is
related to spiral shocks in the accretion disc resulting in an enhanced
accretion rate heating two localised regions on the white dwarf, with the
structure of the shocks fixed in the binary frame explaining the period of the
double humps. The physical origin of the 8.5 h brightenings is less clear.
However, the correlation between the observed variations of the amplitude and
phase of the double-humps with the occurrence of the brightenings is supportive
of an origin in thermal instabilities in the accretion disc.
We present high-time-resolution photometry and phase-resolved spectroscopy of
the short-period ($P_mathrm{orb} = 80.52,mathrm{min}$) cataclysmic variable
SDSS J123813.73-033933.0, observed with the $mathit{Hubble}$ $mathit{Space}$
$mathit{Telescope}$ $mathit{(HST)}$, the $mathit{Kepler/K2}$ mission and the
Very Large Telescope (VLT). We also report observations of the first detected
super-outburst. SDSS J1238-0339 shows two types of variability: quasi-regular
brightenings recurring every $simeq 8.5$ h during which the system increases
in brightness by $simeq 0.5$mag, and a double hump quasi-sinusoidal modulation
at the orbital period. The detailed $mathit{K2}$ light curve reveals that the
amplitude of the double-humps increases during the brightenings and that their
phase undergoes a $simeq 90^{circ}$ phase shift with respect to the quiescent
intervals. The $mathit{HST}$ data unambiguously demonstrate that these
phenomena both arise from the heating and cooling of two relatively large
regions on the white dwarf. We suggest that the double-hump modulation is
related to spiral shocks in the accretion disc resulting in an enhanced
accretion rate heating two localised regions on the white dwarf, with the
structure of the shocks fixed in the binary frame explaining the period of the
double humps. The physical origin of the 8.5 h brightenings is less clear.
However, the correlation between the observed variations of the amplitude and
phase of the double-humps with the occurrence of the brightenings is supportive
of an origin in thermal instabilities in the accretion disc.
http://arxiv.org/icons/sfx.gif
